Apparatus and method for ranging and noise reduction of low coherence interferometry LCI and optical coherence tomography OCT signals by parallel detection of spectral bands

Abstract

Apparatus and method for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry ("LCI") signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source is split into N spectral bands. The N spectral bands are individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band is detected by a separate photo detector and amplified. For each spectral band the signal is band pass filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is reduced by a factor equal to the number of spectral bands. The signal remains the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

The invention claimed is: 
     
       1. An apparatus for optical imaging, comprising:
 a) an interferometer providing at least one signal; 
 b) a spectral separating unit which splits the at least one signal received from the interferometer into a plurality of optical frequencies; 
 c) a plurality of detectors, each detector being configured to detect at least a portion of the optical frequencies received from the spectral separating unit; and 
 d) an arrangement which is configured
 track a phase of the signal of the interferometer. 
 
 
     
     
       2. The apparatus according to  claim 1 , wherein the arrangement reconstructs the signal from the detectors by the mathematical manipulation. 
     
     
       3. The apparatus according to  claim 1 , wherein the spectral separating unit comprises the at least one of (i) an addressable mirror array or (ii) a waveguide filter. 
     
     
       4. The apparatus according to  claim 1 , wherein the spectral separating unit splits the signal into the bands. 
     
     
       5. The apparatus according to  claim 1 , wherein the detectors are provided in a form of a two-dimensional array. 
     
     
       6. The apparatus according to  claim 1 , wherein a sample is scanned in a series of simultaneous illuminations of substantially all of areas of the sample to provide at least one radiation associated with the sample to be used by the interferometer to provide the at least one signal. 
     
     
       7. The apparatus according to  claim 1 , wherein the spectral separating unit comprises a polarization separating unit. 
     
     
       8. The apparatus according to  claim 1 , wherein the interferometer comprises an arrangement generating a path length difference that is a fraction of a ranging depth of the interferometer. 
     
     
       9. The apparatus according to  claim 1 , wherein the interferometer receives at least one electromagnetic radiation from a transmissive reference, and generates the at least one signal as a function of the at least one electromagnetic radiation. 
     
     
       10. An apparatus for tracking a phase of at least one electro-magnetic signal generated by an interferometer so as to reduce an attenuation of the at least one signal due to its fringe instability, comprising:
 a processing arrangement configured to: 
 a. receive information associated with the at least one signal, 
 b. adjust the phase of the at least one signal, 
 c. obtain a position of a signal section of the at least one signal, 
 d. modify at least one characteristic of the at least one signal if the position of the signal section is provided away from a peak of the at least one signal by more than a predetermined distance, and 
 e. repeat steps (c) and (d) until the at least one signal is within the predetermined distance from the peak. 
 
     
     
       11. The apparatus according to  claim 10 , wherein the information corresponds to a combination of at least one of the spectral bands which are separated from the at least one electromagnetic signal by a spectral separating arrangement. 
     
     
       12. A logic arrangement for tracking a phase of at least one electro-magnetic signal generated by an interferometer so as to reduce an attenuation of the at least one signal due to its fringe instability, which, when executed by a processing arrangement, configures the processing arrangement to perform procedures execute the comprising of:
 a) receiving information associated with the at least one signal; 
 b) adjusting the phase of the at least one signal; 
 c) obtaining a position of a signal section of the at least one signal; 
 d) modifying at least one characteristic of the at least one signal if the position of the signal section is away from a peak of the at least one signal by more than a predetermined distance; and 
 e) repeating steps (c) and (d) until the at least one signal is within the predetermined distance from the peak. 
 
     
     
       13. A method for tracking a phase of at least one electromagnetic signal generated by an interferometer so as to reduce an attenuation of the at least one signal due to its fringe instability, comprising:
 a) receiving information associated with the at least one signal; 
 b) adjusting the phase of the at least one signal; 
 c) obtaining a position of a signal section of the at least one signal; 
 d) modifying at least one characteristic of the at least one signal if the position of the signal section is away from a peak of the at least one signal by more than a predetermined distance; and 
 e) repeating steps (c) and (d) until the at least one signal reaches a further position that is within the predetermined distance from the peak. 
 
     
     
       14. A storage medium including executable instructions thereon for tracking a phase of at least one electromagnetic signal generated by an interferometer so as to reduce an attenuation of the at least one signal due to its fringe instability, wherein, when the executable instructions are executed by a processing system, the executable instructions configure the processing system to perform procedures comprising:
 a) receiving information associated with the at least one signal; 
 b) adjusting the phase of the at least one signal; 
 c) obtaining a position of a signal section of the at least one signal; 
 d) modifying at least one characteristic of the at least one signal if the position of the signal section is away from a peak of the at least one signal by a predetermined distance; and 
 e) repeating steps (c) and (d) until the at least one signal is within the predetermined distance from the peak.